There is a growing need for siloxane polymers that are hydrophilic and can be made to dissolve in water or act as amphoteric surfactants in aqueous solutions. One chemical modification method to enhance the hydrophilic properties of polysiloxanes is to graft copolymerize polysiloxanes with polyethers. This chemical modification was extensively used to prepare various silicone surfactants.
However, it commonly involves ethoxylatian or propoxylation of the polymer backbone, using ethylene oxide or propylene oxide and requires special equipment and facilities due to the toxic and explosive nature of the oxides.
Another common method is to hydrosilylate polysiloxanes containing methyl hydrogen radicals with vinyl terminated hydrophilic polyethers as published in “Silicone Surfactants” by Randal M. Hill, Ed. Surfactant Science Series Vol. 86, Marcel Dekker Pub. New York, N.Y., 1999. The copolymer products of this reaction are useful as surfactants and their hydrophilic-lipophilic balance (HLB) is directly related to the ratio of the hydrophobic siloxanes to the hydrophilic ether composition. However, this method is deficient since increasing the polyether content in the copolymers in order to increase the water solubility leads to lower polysiloxane content and a loss of the other desirable polysiloxane inherent properties.
Introduction of various hydrophilic functional groups such as quaternary ammonium salts (QAS) or hydroxyalkyl groups have also been used to enhance the hydrophilic properties of polysiloxanes. Here too, increasing the content of these groups will increase the hydrophilic nature of the polysiloxane. This method is effective but the solubility of such polysiloxanes greatly depends on the pH of the water and any additive present in the aqueous solution. Similarly, introduction of amine or carboxylic pendant radicals onto the silicone polymer chain that will form soluble salts in aqueous acid or alkaline solutions, respectively, is known to enhance the hydrophilicity of these polysiloxanes.
For example, U.S. Pat. No. 4,895,964 to Margida, Jan. 23, 1990 discloses a process for the manufacture of quaternary ammonium pendant siloxane copolymers by the reaction of epoxy pendant siloxane copolymers with a tertiary amine acid salt.
U.S. Pat. No. 5,593,611 to Czech, Jan. 14, 1997, U.S. Pat. No. 6,346,593 to Hupfield, Feb. 12, 2002 and U.S. Pat. No. 6,153,717 to Chung, Nov. 28, 2000 disclose the preparation of aminopolysiloxanes. The aminopolysiloxanes are conveniently prepared by hydrolyzing and condensing amino-functional dialkoxysilanes with water in the presence of heat and a base catalyst. However, as such these amino-functional polysiloxane are hydrophobic. There are only a few examples in the prior art where amino-functional polysiloxanes were further reacted to enhance the hydrophilic nature of polysiloxanes.
U.S. Pat. No. 4,757,121 to Tanaka et al., Jul. 12, 1988, discloses an amino-substituted organopolysiloxane that contains hydroxyl groups or alkoxy groups. This polysiloxane was reacted with epoxy-containing alkoxysilanes to form a crosslinked film.
U.S. Pat. No. 5,100,991 to Cray, Feb. 22, 1996, discloses compounds that were prepared by the reaction of an aminofunctional silane or siloxane with a lactone.
EP A2 0 399 706 by Cray, published on Nov. 28, 1990, discloses a method for preparing a treatment agent for fibrous materials by hydroxyl-functional polysiloxanes that were prepared from the reaction of amine-containing organosiloxane with a monoepoxide. The resulting product had primary, secondary, and tertiary amine groups.
Polyhydroxyl silanes or siloxanes are disclosed in U.S. Pat. No. 4,591,652 to DePasquale, May 27, 1986. These compounds were obtained by reacting an amine terminated silane, preferably an amine terminated polyalkoxysilane, with an aldonic acid lactone in the presence of an alcohol under inert atmosphere. The preferred aldonic acid lactone in this patent is δ-gluconolactone. The water soluble products from this disclosure were claimed to be useful as insoluble coatings for various substrates.
It is the object of the present disclosure to provide polysiloxanes containing multiple pendant or terminal carbinol functional groups connected to carbamate functional groups that enhances the hydrophilic nature of the polysiloxanes. It is further the objective of this disclosure to provide examples of using these polysiloxanes as film coatings with desirable surface properties, intermediates in the manufacturing in polyurethane and polyester manufacturing, as well as their use as amphotheric surfactants in aqueous solutions.